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Join Date: Oct 2009
Posts: 20
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cylinder wear tolerances
Could someone fill me in on cylinder wear tolerances on stock 1996 to 1998 993 cylinders.
Thank You |
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09-29-2010, 12:06 AM
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Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
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I would kindly recommend measuring your piston to cylinder wall clearances (in several places).
The cylinders "ovalize" more than they actually wear unless its swallowed a load of dirt from a bad air filter.
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Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com |
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09-29-2010, 10:31 AM
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Location: CT
Posts: 11,538
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The factory wear limit for cylinders is generally 0.1 mm above nominal size. For a 100 mm cylinder the wear limit would be around 100.1 mm. As Steve says, you rarely find a cylinder worn above the wear limit. The ovality limit is 0.04 mm and is more likely to be a problem than overall wear. Matching the piston diameter to the cylinder diameter to achieve proper clearances is also important.
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Tom Butler 1973 RSR Clone 1970 911E 914-6 GT Recreation in Process |
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09-29-2010, 11:50 AM
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What happens if a piston is used that has smaller clearance to the cylinder walls then normal. Not jamed in there but half the recommended clearence.
Chris 73 911 E |
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10-03-2010, 04:51 PM
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Location: London Ont Canada
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If it is at the low limit it should be OK but any tighter then you run the risk of scuffing and early failure when it gets hot.
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1980 911 SC 3.6 coupe sold 1995 993 coupe 1966 Mustang Shelby clone 1964 Corvair Spyder Turbo gone 2012 Boss 302 |
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10-03-2010, 06:56 PM
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Location: Phoenix Arizona
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Actually the greater danger with Nikasil cylinders is to cold seize a piston in the cylinder, the clearances open up quite a bit as the cylinder heats up. I have had good luck running the skirt to wall down to.0011 inch with JE pistons with a hard dry film lubricant coating on the skirts in Nikasil cylinders.
aws |
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10-04-2010, 08:23 PM
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Join Date: Sep 2007
Posts: 500
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Oter
From the 993 Tech Spec book Engine M64/05/06/07/08 Play: Cylinders-Pistons 0.02 - 0.03 (new condition) Engine M64/20 RS Play: Cylinders - Pistons 0.04 - 0.05 (new condition) And from both the 993 & 964 Factory Workshop Manuals Cylinder-to-piston clearance 0.02 -0.03 |
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10-05-2010, 01:41 PM
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